The present invention relates to a driving state monitoring apparatus for vehicles, which monitors a driving state of the driver of the vehicle and issues an alarm as required.
The driving state of a driver is related to the driving ability of that driver and can be lowered due to fatigue, dozing, etc.
A prior art driving state monitoring apparatus is known which has means for estimating the response delay time of the driver and the deviation between a vehicle position and the running lane according to the amount of steering of the vehicle and the vehicle speed. The apparatus also includes means for comparing the estimated response delay time of the driver and the estimated deviation with a response delay time and a deviation in a normal condition, respectively, and means for determining the driving state of the driver (e.g., an abnormal steering caused by a lowered driving ability due to dozing or fatigue of the driver) (Japanese Patent Laid-open No. Hei 5-85221).
Another prior art driving state monitoring apparatus is known, having means for detecting the yaw rate and the vehicle speed, means for obtaining a reference line for running of the vehicle according to the detected yaw rate and the detected vehicle speed, and means for determining abnormality of the driving state of the driver by using a parameter indicative of the deviation between an actual running locus and the reference line (Japanese Patent Laid-open No. Hei 8-249600).
However, in the above-mentioned conventional monitoring apparatus described in Japanese Patent Laid-open No. Hei 5-85221, the deviation between the actual vehicle position and the running lane (reference vehicle position) is calculated according to the amount of steering and the vehicle speed, but not according to a physical quantity relating directly to vehicle behavior. Accordingly, an error in this deviation can be produced because of changes in vehicle characteristics (e,g., characteristics of the vehicle suspension or the steering device), causing a reduction in accuracy of the determination of the driver""s driving state.
On the other hand, in the monitoring apparatus described in Japanese Patent Laid-open No. Hei 8-249600, the driving state is determined by using a yaw rate relating directly to vehicle behavior, thereby improving the determination accuracy. However, because the driving state is determined only according to the parameter indicative of the deviation between the running locus and the reference line, this prior art apparatus lacks the necessary accuracy.
It is accordingly an object of the present invention to provide a driving state monitoring apparatus which can determine the behavior of a vehicle more precisely than the prior art systems, thereby providing a precise determination of the driving state.
According to the present invention, a driving state monitoring apparatus for a vehicle, for monitoring the driving state of a driver of the vehicle is provided. The apparatus comprises behavior parameter detecting means for detecting a behavior parameter indicative of a lateral movement of the vehicle; vehicle speed detecting means for detecting a vehicle speed of the vehicle; behavior reference setting means for setting a behavior reference according to changes in the behavior parameter; running locus calculating means for calculating a running locus of the vehicle according to the behavior parameter, the behavior reference, and the vehicle speed; vehicle behavior feature parameter calculating means for calculating a plurality of vehicle behavior feature parameters indicative of the feature of vehicle behavior according to the running locus; and driving state determining means for determining whether or not the driving state of the driver is proper according to the plurality of vehicle behavior feature parameters.
With this arrangement, a behavior reference is set according to changes in the behavior parameter indicative of the lateral movement of the vehicle; a running locus of the vehicle is estimated according to the behavior parameter, the behavior reference, and a vehicle speed; a plurality of vehicle behavior feature parameters indicative of the feature of vehicle behavior are calculated according to the running locus; and it is determined whether or not the driving state by the driver is proper according to the plural vehicle behavior feature parameters calculated above. Accordingly, the vehicle behavior can be grasped more precisely over the prior art, thereby effecting precise determination of the driving state.
Preferably, the driving state determining means stepwise determines the abnormality of the driving state according to the plurality of vehicle behavior feature parameters.
Preferably, the behavior reference setting means obtains a simple regression line according to changes in the behavior parameter and sets the simple regression line as the behavior reference.
Preferably, the vehicle behavior feature parameter calculating means calculates at least two parameters of a lateral deviation behavior quantity (LOCWIDTH) which indicates lateral deviation of the running locus with respect to the behavior reference, the number of occurrences (NP) that the absolute value of a fluctuation quantity with respect to the behavior reference exceeds a predetermined fluctuation width (xcex94h) in a predetermined measurement time period (T1), the ratio of a maximum fluctuation quantity (LOCWIDTH1) on the plus side with respect to the behavior reference and a maximum fluctuation quantity (LOCWIDTH2) on the minus side with respect to the behavior reference, and the ratio of a maximum length (LOCLEN1) of a plus region along a vehicle running direction where the running locus fluctuates on the plus side with respect to the behavior reference and a maximum length (LOCLEN2) of a minus region along the vehicle running direction where the running locus fluctuates on the minus side with respect to the behavior reference.
Preferably, road shape determining means for determining the shape of a road on which the vehicle is running is further included, and when the road shape determining means determines that the road is substantially straight or curved with a substantially constant radius of curvature, and the driving state determining means determines that the driving state of the driver is not proper, it is determined that the driving state of the driver is abnormal.
Preferably, the road shape determining means estimates the radius of curvature of the road on which the vehicle is running and determines the shape of the road according to the estimated radius of curvature and a change rate of the estimated radius of curvature.
Preferably, the road shape determining means estimates the radius of curvature according to the vehicle speed and a regression coefficient of the simple regression line.
Preferably, the driving state determining means sets a threshold for use in determining whether or not the driving state is proper, according to the vehicle speed and the estimated radius of curvature of the road.
Preferably, the driving state determining means calculates a statistic including at least a mean value from a plurality of measured data of a lateral deviation behavior quantity which indicates lateral deviation of the running locus with respect to the behavior reference, and sets a threshold for use in determining whether or not the driving state is proper, according to the calculated statistic.
Preferably, the driving state determining means determines whether or not the driver intends to make a lane change, and when the driving state determining means determines that the driver does not intend to make the lane change and that the driving state is not proper, it is determined that the driving state of the driver is abnormal.
Preferably, the vehicle behavior feature parameter calculating means calculates the lateral deviation of the running locus with respect to the behavior reference and calculates a maximum amplitude of the lateral deviation in a predetermined time period as the lateral deviation behavior quantity.
Preferably, the vehicle behavior feature parameter calculating means calculates the area of a region surrounded by the running locus and the simple regression line as the lateral deviation behavior quantity.
Other objects and features of the invention will be more fully understood from the following detailed description and appended claims when taken with the accompanying drawings.